To prepare the pesto: in a food processor, combine olives, parmesan cheese, parsley, garlic and pepperoncini and blend 1 minute. With motor running, slowly pour in olive oil until a thick, smooth paste is formed. Allow to stand 1/2 hour before using.
To make the crust: After the dough has risen, punch it down and place it back on the floured surface. This amount of dough yielded 2 pizza crusts for my 12-inch cast iron skillet. But I stuffed the crust with cheese, so if you skip this step make your crust on the thicker side. If you're using an 8-inch skillet, you may get 3 crusts. Divide the dough evenly in half (or thirds). Roll out your dough just a little larger than the size of your skillet. Place on a large sheet of parchment paper and then place on a pizza peel or large pan flipped upside down. Instead of using parchment paper you can just place the dough on an extremely well floured pizza peel, but I found it was easier to be able to lift the pizza into the pan rather than sliding it in (my toppings fell of first try). Once your dough is on the peel place half to three fourths of the feta cheese around the outer edge of the dough. Roll the edges up and over the cheese pinching the dough to seal in the cheese.
To make the pizza: Place an oven rack directly under your broiler and preheat your broiler to the highest setting. Additionally, place your cast iron skillet on the stovetop burner, turning the heat on high. You want to heat the skillet for 10 minutes. If it begins to smoke a lot, you can reduce the heat a bit. But you want it HOT.
While the skillet is heating, begin placing your toppings on your dough. Remember, the dough MUST be on a well-floured pizza peel (or use parchment paper) so you can simply slide the entire thing into the skillet. Spread all of the pesto on one dough round. Top with shredded mozzarella cheese, roasted red peppers and the remaining feta cheese. Place a potholder or thick towel on the handle of the skillet (it will be sooo hot). Carefully slide the pizza into the skillet (or if using the parchment paper carefully lift the pizza and place in the pan), dough side down. After about 30 seconds, turn off the burner, grab the skillet and pop it in the oven, right under the broiler. Broil for 1 minute, then using the potholder, grab the handle and rotate 180 degrees, broiling for only 1 more minute. Remove immediately and place on the stovetop. Top with fresh basil and let cool slightly for about 5 minutes, then use a large spatula or carefully slide the pizza out to remove and drizzle with balsamic reduction.
To roast your own red peppers you can either broil one in the oven or place it directly on a gas top burner and char all sides of the pepper. Once all sides are charred remove the pepper from the broiler or stove top and place in a bowl and cover. Allow to sit for 5 minutes and remove and peel the charred parts away. Slice and use. Balsamic glaze can be purchased in the Italian aisle of most grocery stores, or you can also make it yourself by simply reducing 1 cup of balsamic vinegar with a spoonful of brown sugar until thick and syrupy.